This is really an unique book which should be read by everyone who is interested in the foundations of modern physics from a philosophical point of view or anyone who is working in the modern fields of quantum optics and quantum information. (Anton Zeilinger, University of Vienna)Stenholm, a theoretical physicist specialising in quantum optics, has a wide understanding of many of the philosophical issues that lie at the heart of the debate that surrounds the foundations of quantum theory. (Basil Hiley, Birkbeck College, University of London)